Apparatus and method for fluorescence grading of gemstones

ABSTRACT

Provided herein is an apparatus for assessing a fluorescence characteristic of a gemstone. The apparatus comprises an optically opaque platform for supporting a gemstone to be assessed, one or more light source to provide uniform UV and non-UV illumination, an image capturing component, and a telecentric lens positioned to provide fluorescent images of the illuminated gemstone to the image capturing component. Also provided are methods of fluorescence analysis based on images collected using such an apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/673,780 filed Mar. 30, 2015 and entitled“Apparatus and Method for Fluorescence Grading of Gemstones,” thecontent of which is incorporated herein by reference in its entirety

FIELD

The apparatus and methods disclosed herein generally relate tofluorescence grading of gemstones, in particular cut gemstones. Inparticular, the apparatus and methods relate to fluorescence grading ofcut gemstones of irregular or fancy shapes. The apparatus and methodsdisclosed herein further relate to digital image processing based oncolor component analysis.

BACKGROUND

Diamonds and other gemstones are often analyzed and graded by multipletrained and skilled individuals, based upon their visual appearance. Forexample, the foundation of diamond analysis comprises analysis of theFour C's (color, clarity, cut and carat weight), two of which, color andclarity, have been traditionally evaluated by human inspection.Gemstones are also assessed for unusual visual qualities. For example,certain gemstones produce fluorescence emission under UV illumination,the extent and distribution of such fluorescence are also used to gradesuch gemstones. Like color and clarity grading, fluorescence grading waspreviously primarily assessed based on human visual perception. Analysisand grading requires the exercise of judgment, the formation of opinionsand the ability to draw fine distinctions based on visual comparisons.

A process of inspection and analysis is often time-consuming, involvingmultiple rounds of inspections, measurements and checks by each trainedand experienced individual. The process also involves quality controland may include a variety of non-destructive tests to identifytreatments, fillings or other defects that may affect the quality of aspecimen. Finally, the process includes intensive visual comparison ofthe diamond with a reference set of diamond master stones that serve asa historical standard with respect to diamond color and fluorescence.

Instruments have been created to improve efficiency and to permitgemstone analysis in the absence of trained and experienced individuals.For example, U.S. Pat. No. 7,102,742 to Geurtz et al. discloses agemstone fluorescence measuring device that includes an ultraviolet(“UV”) emission chamber, a UV radiation source, and a light meterassembly. The UV radiation source includes an upper light emitting diode(“LED”) and a lower LED that radiate a gemstone under test from bothabove and below the gemstone. However, current instrument cannot provideconsistent and reproducible fluorescence grade to fancy shape cutstones; such gemstones that are classified as Step Cuts, Hearts,Marquises, Ovals, Pears, Triangles, Princess cut, or any other cutsrather than round brilliant cut (RBC). Additionally, current instrumentcannot provide hue information and an operator must input the color offluorescence manually. This leads to the incorrect grading since it isnot easy to see the color of weak fluorescence by human eyes.

What is need are apparatus and methods that can provide gemstoneassessment and grading (e.g., fluorescence grading) as consistent andaccurate as assessment and grading provided by trained and experiencedindividuals.

SUMMARY

In one aspect, provided herein is an apparatus for assessing afluorescence characteristic of a gemstone. The apparatus comprises anoptically opaque platform, where the platform has a surface configuredto support a gemstone to be assessed; a light source shaped to at leastpartially enclose the platform, where the light source is about the samelevel as or below the surface of platform and designed to provideuniform ultraviolet (UV) radiation to the gemstone on the platform; animage capturing component, where the image capturing component ispositioned at a predetermined angle relative to the platform surfacethat supports the gemstone, and where the image capturing component andplatform are configured to rotate relative to each other; and atelecentric lens positioned to provide an image of the illuminatedgemstone to the image capturing component.

In one aspect, provided herein is an apparatus for assessing a colorcharacteristic of a gemstone. The apparatus comprises an opticallyopaque platform, where the platform has a surface configured to supporta gemstone to be assessed; a light source above the surface of theplatform, where the light source is designed to provide uniformultraviolet (UV) radiation to the gemstone on the platform; an imagecapturing component, where the image capturing component is positionedat a predetermined angle relative to the platform surface that supportsthe gemstone, and where the image capturing component and platform areconfigured to rotate relative to each other; and a telecentric lenspositioned to provide an image of the illuminated gemstone to the imagecapturing component.

In some embodiments, the apparatus further comprises a collimation lens,where the collimation lens and the light source are coupled to provideuniform UV illumination to the gemstone on the platform.

In some embodiments, the apparatus further comprises an opticaldiffuser, wherein the optical diffuser and the light source are coupledto provide uniform UV illumination to the gemstone on the platform.

In some embodiments, the apparatus further comprises a collimation lens,and an optical diffuser, where the collimation lens, optical diffuserand the light source are coupled to provide uniform UV illumination tothe gemstone on the platform.

In some embodiments, the apparatus further comprises a reflector devicehaving an inner surface that is at least partially spherical andcomprises a reflective material. The reflector device at least partiallycovers the light source and platform surface, and directs UV radiationfrom the light source towards the gemstone positioned on the platformsurface. In some embodiments, the inner surface of the reflector devicehas a hemispherical shape.

In some embodiments, the apparatus further comprises a computer readablemedium for storing the images collected by the image capturingcomponent.

In some embodiments, the apparatus further comprises an interfacebetween the light source and platform surface for adjusting the outputintensity of the UV radiation.

In some embodiments, the apparatus further comprises a UV filter betweenthe image capturing component and the telecentric lens to eliminate allUV components.

In some embodiments, the UV radiation provided by the light sourcecomprises trans-radiation, direct-UV radiation, and a combinationthereof.

In some embodiments, the light source further provides uniform non-UVillumination to the gemstone.

In some embodiments, the telecentric lens is an object-space telecentriclens or a double telecentric lens.

In some embodiments, the platform is configured to rotate around arotational axis that is perpendicular to the side of the platform wherethe gemstone is positioned.

In some embodiments, the platform is configured to rotate 360 degreesaround the rotational axis.

In some embodiments, the platform is a flat circular platform, andwherein the rotational axis is through the center of the circularplatform.

In some embodiments, the platform surface comprises a UV reflectivematerial.

In some embodiments, the platform surface comprises a diffuse UVreflective material.

In some embodiments, the platform surface comprises a white diffusereflective material.

In some embodiments, the light source is configured as a ring lightsurrounding the platform surface. In some embodiments, the light sourcecomprises a plurality of light emitting LEDs. In some embodiments, theLEDs emits fluorescence at 365 nm or 385 nm.

In some embodiments, the LEDs are coupled with a bandpass filter. Insome embodiments, the bandpass filter is set at 365 nm or 385 nm.

In some embodiments, the LEDs are configured as a ring light surroundingthe platform surface.

In some embodiments, the light source comprises a daylight approximatinglight source and a plurality of light emitting LEDs. In someembodiments, the LEDs are coupled with a bandpass filter. In someembodiments, the bandpass filter is set at 365 nm or 385 nm.

In some embodiments, the predetermined angle between the image capturingcomponent and the platform surface is between approximately zero andapproximately 45 degrees. In some embodiments, the predetermined anglebetween the image capturing component and the platform surface isbetween approximately 10 and approximately 35 degrees.

In some embodiments, the image capturing component is selected from thegroup consisting of a color camera, a CCD camera, and one or more CMOSsensors.

In some embodiments, the image capturing component a plurality of colorimages of the gemstone illuminated by UV radiation, each imagecomprising a full image of the gemstone.

In some embodiments, the image capturing component captures a pluralityof color images of the illuminated gemstone, where each image is takenwhen the image capturing component and the platform surface are at adifferent relative rotational position, and wherein each image comprisesa full image of the gemstone.

In some embodiments, the plurality of color images comprises 4 or morecolor images, 5 or more color images, 10 or more images, 15 or moreimages, 20 or more images, or 800 or more images, and wherein each imageis taken at a unique image angle and comprises a plurality of pixels.

In some embodiments, the fluorescence characteristic is a fluorescenceintensity level, a fluorescence color, or a combination thereof.

In one aspect, provided herein is a method of assessing a fluorescencecharacteristic of a sample gemstone. For example, the method comprisesthe steps of (i) determining a fluorescence mask for a fluorescent imagein a plurality of fluorescent images based on an outline mask determinedfrom an image in a plurality of images and an apparent fluorescence areabased on the fluorescent image, (ii) quantifying individual colorcomponents in each pixel in the fluorescence mask in the fluorescentimage of the plurality of fluorescent images, thereby converting valuesfor individual color components to one or more parameters representingthe color characteristic of each pixel; (iii) determining an averagevalue for each of the one or more parameters for all pixels in thedefined area in all images of the plurality of fluorescent image; and(iv) calculating a first fluorescence score of a sample gemstone basedon the average values of the one or more parameters of all pixels in thedefined area in all images of the plurality of fluorescent images.

Here, each image of the plurality of images comprises a full image ofthe sample gemstone being illuminated by non-UV light source. Each imageof the plurality of fluorescent images comprises a full image of thesample gemstone being illuminated by uniform UV light source. Inaddition, the image and the fluorescent image are captured underidentical conditions except the illumination light source;

In some embodiments, the method further comprises a step of (v)calculating a second fluorescence score of a sample gemstone based onpixels in the outline masks for all images of the plurality offluorescent images.

In some embodiments, the method further comprises a step of (vi)assessing the fluorescence characteristic of the sample gemstone bycomparing the first or second fluorescence score to values ofcorresponding fluorescence scores of one or more control fluorescencegemstones which are previously determined.

In some embodiments, the first fluorescence score reflects the color ofthe fluorescence and wherein the second fluorescence score reflects thestrength.

In some embodiments, the method further comprises a step of collectingthe plurality of images of the sample gemstone using an image capturingcomponent at uniquely different image rotational angles whilemaintaining a constant image view angle.

In some embodiments, the method further comprises a step of collectingthe plurality of fluorescent images of the sample gemstone using animage capturing component at uniquely different image rotational angleswhile maintaining a constant image view angle. Here, each fluorescentimage in the plurality of fluorescent images corresponds to an image inthe plurality of image and both are captured under identical imagerotational angle and image view angle.

In some embodiments, the method further comprises a step of determininga fluorescence mask for each fluorescent image in the plurality offluorescent images.

In some embodiments, the method further comprises a step of quantifyingindividual color components in each pixel in the fluorescence mask ineach fluorescent image of the plurality of fluorescent images.

In some embodiments, the method further comprises the steps ofcollecting a new plurality of fluorescent images of the sample gemstoneusing the image capturing component at the uniquely different imagerotational angles while maintaining the constant image view angle,wherein there is a time gap between the time when the plurality offluorescent images is collected and the time when the new plurality offluorescent images is collected; assigning a new fluorescent grade basedon the new plurality of fluorescent images by applying steps (i) through(vi); and comparing the fluorescent grade and the new fluorescent gradebased on the time gap.

In some embodiments, the time gap is between 2 minutes and 5 hours.

One of skill in the art would understand that any embodiment describedherein can be used, when applicable, in connection with any aspect ofthe apparatus or method.

BRIEF DESCRIPTION OF THE DRAWINGS

Those of skill in the art will understand that the drawings, describedbelow, are for illustrative purposes only. The drawings are not intendedto limit the scope of the present teachings in any way.

FIG. 1 depicts an exemplary embodiment of a gemstone optical assessmentsystem including an optical unit and a gemstone evaluation unit.

FIG. 2A depicts an exemplary schematic embodiment of a gemstone opticalassessment system in a closed configuration (light source not shown).

FIG. 2B depicts an exemplary schematic embodiment of a gemstone opticalassessment system in an opened configuration (light source not shown).

FIG. 3 depicts an exemplary embodiment of a sample platform withsurrounding ring light illumination.

FIG. 4 depicts an exemplary schematic illustrating image view angle andimage rotational angle.

FIG. 5A depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 5B depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 5C depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 5D depicts an exemplary embodiment of a top reflector with internalreflective surface.

FIG. 6A depicts an exemplary embodiment of a connector module forlinking a gemstone evaluation unit and an optic unit.

FIG. 6B depicts an exemplary embodiment of a connector module forlinking a gemstone evaluation unit and an optic unit.

FIG. 6C depicts an exemplary embodiment of a connector module forlinking a gemstone evaluation unit and an optic unit.

FIG. 7A depicts an exemplary embodiment, showing a RBC diamond beingilluminated by daylight approximating light source.

FIG. 7B depicts an exemplary embodiment, showing an image of a RBCdiamond being illuminated by daylight approximating light source afteran outline mask is applied.

FIG. 7C depicts an exemplary embodiment, showing extraction of anoutline mask.

FIG. 7D depicts an exemplary embodiment, showing extraction of anapparent fluorescence area.

FIG. 7E depicts an exemplary embodiment, showing extraction of anoutline mask.

FIG. 7F depicts an exemplary embodiment, showing extraction of anapparent fluorescence area.

FIG. 8 depicts an exemplary organization of a computer system.

FIG. 9A depicts an exemplary process for a data collection and analysis.

FIG. 9B depicts an exemplary process for a data collection and analysis.

FIG. 9C depicts an exemplary process for a data collection and analysis.

FIG. 10 depicts exemplary images taken under regular illumination and UVillumination.

FIG. 11 depicts an exemplary embodiment, illustrating differentstrengths in fluorescence emission.

FIG. 12 depicts an exemplary embodiment, illustrating inhomogeneousfluorescence emission.

FIG. 13 depicts an exemplary embodiment, illustrating fluorescenceemission in gemstones of different shapes.

FIG. 14 depicts an exemplary embodiment, illustrating fluorescenceemission in different colors.

FIG. 15 depicts an exemplary embodiment, illustrating fluorescenceemission in different colors.

DETAILED DESCRIPTION

Unless otherwise noted, terms are to be understood according toconventional usage by those of ordinary skill in the relevant art. Forillustration purposes, diamonds are used as the representativegemstones. One of skill in the art would understand that theapparatuses, systems and methods disclosed herein are applicable to alltypes of gemstones capable of emitting fluorescence upon UV exposure.Systems and methods for color grading based on similar apparatuses aredisclosed in U.S. patent application Ser. No. 14/673,776 (U.S. Pat. No.9,678,081), entitled “APPARATUS AND METHOD FOR ASSESSING OPTICAL QUALITYOF GEMSTONES” and filed on Mar. 30, 2015 concurrently herewith, which ishereby incorporated by reference herein in its entirety.

As noted in the background, current automated instrument fails toprovide accurate, complete and consistent assessment of the fluorescenceproperty of certain gemstones (such as those of irregular or fancyshapes). One reason to account for the failure is that fluorescenceintensity of a gemstone is affected significantly by a number of factorssuch as the orientation of the gemstone in relation to the detector, theposition of gemstone, and the size of gemstone. In addition, somegemstones exhibit inhomogeneous distribution of fluorescence and currentinstrument cannot provide reproducible fluorescence grade for suchstones, even if the gemstones are of regular round brilliant cut (RBC).

In order to overcome the existing issues, an improved fluorescencegrading instrument as disclosed herein has the followingcharacteristics: (1) to provide consistent and reproducible fluorescencegrade to gemstones with no limitation from their sizes and shapes (2) toprovide consistent and reproducible fluorescence color; (3) to provideconsistent and reproducible fluorescence grade with easy and quickoperation (e.g., operators do not need to put stones in the sameposition).

In one aspect, provided herein is an improved fluorescence gradingapparatus for fluorescence assessment of gemstones such as cut diamonds.The apparatus is suitable for grading gemstones such as cut diamonds,including gemstones of irregular shapes, sizes, colors, and fluorescencedistribution. An exemplary apparatus 100 is illustrated in FIG. 1, whichincludes but is not limited to, for example, a gemstone evaluationcomponent 10, a light source with a UV filter 20, a telecentric lens 30,and an image capturing component 40.

Based on functionality, the components of an apparatus disclosed hereincan be divided into two main units: a gemstone presentation unit and anoptical unit. The gemstone presentation unit provides uniformillumination to gemstones being analyzed and the optical unit capturesimages of gemstones being presented.

Additionally and not depicted in FIG. 1, an exemplary apparatus furthercomprises a computer processing unit for analyzing information collectedby the image capturing component.

As illustrated in FIG. 1, an exemplary gemstone presentation unit inturn comprises at least two parts: gemstone evaluation component 10 anda light source 20. The gemstone evaluation component is where a gemstoneis presented. As depicted in FIGS. 2A and 2B, the gemstone evaluationcomponent has a closed and an open configuration. Here, in order toclearly illustrate the different configurations, light source 20 isomitted in FIGS. 2A and 2B. In the closed configuration (see, e.g., FIG.2A), a gemstone subject to analysis is completely concealed and notvisible from an observer. In some embodiments, in order to avoid theinconsistencies caused by ambient light or other light, gemstoneevaluation component is isolated and closed system from which ambientlight or other light is excluded. The gemstone evaluation component andoptic unit are joined in a complementary manner such that ambient lightor other light is excluded from a concealed sample chamber within whicha sample gemstone is housed. Although the fluorescence light source isnot depicted in FIGS. 2A and 2B, one of skill in the art wouldunderstand that such as light source is required for fluorescencegrading of gemstones.

Under the closed configuration, image information concerning thegemstone being analyzed is received and captured by the optical unit,which comprises a telecentric lens 30 and an image capturing device 40(e.g., a camera).

In the open configuration (see, e.g., FIG. 2B), no image information iscollected. Instead, the gemstone subject to analysis is exposed to anobserver. In the open configuration, the gemstone presentation unit isrevealed to have two parts: a bottom presentation component 50 and a topreflector component 60. In some embodiments, as illustrated in FIG. 2B,the top reflector component is mounted on movable side tracks. When thetop reflector is moved on these tracks away from the optical unit, thebottom presentation component 50 is exposed. As shown in FIG. 2B, theshape and design of the opening of the top reflector component 60 iscomplementary to the shape and design of the optical connector module(e.g., element 70 in FIG. 2B) of the optical unit. In some embodiments,the optical connector module is a lens hood to which the telecentriclens 30 is attached.

An exemplary bottom presentation component 50 is illustrated in FIG. 3.A circular white reflective platform 510 functions as the base on whicha sample gemstone 520 is placed. A concentric circular ring light 530 isplaced outside the circular platform such that the platform iscompletely enclosed within ring light 530.

Platform 510, also referred to as a stage or sample stage, is criticalfor the system disclosed herein. Importantly, it provides support to agemstone that is being analyzed. In some embodiments, the top surface ofthe platform is a horizontal and flat. In addition, it functions as astage for data collection by telecentric lens 30 and image capturingdevice 40 and subsequent analysis. In order to achieve data consistency,telecentric lens 30 is positioned at a first pre-determined anglerelative to the top surface of platform 510. In some embodiments, imagecapturing device 40 is positioned at positioned at a secondpre-determined angle relative to the top surface of platform 510. Insome embodiments, the first and second pre-determined angles are thesame and it has been optimized for data collection. In some embodiments,the first and second pre-determined angles are different, but each hasbeen optimized for data collection. The first and second pre-determinedangles can be referred to as the image or camera view angle.

An exemplary illustration of the relative configuration of the topsurface of platform 510 to the optical unit (e.g., telecentric lens 30and camera 40) is depicted in FIG. 4. Here, the optical unit, includingboth telecentric lens 30 and image capturing device 40, is positioned ata pre-determined angle (alpha) relative to the platform surface.

In some embodiments, the circular reflective platform is rotatable. Forexample, the platform is mounted on or connected with a rotor. Inpreferred embodiments, a gemstone being subjected to analysis is placedat the center of the platform surface, as illustrated in FIG. 3. Theplatform is then rotated in relation to the optical unit such thatimages of the gemstone at different angles are collected by the imagecapturing device.

In some embodiment, the platform surface is rotated around a rotationalaxis that goes through the center of origin of the circular platformsurface and is perpendicular to the platform surface; see, for example,axis Zz depicted in FIG. 4.

In some embodiments, the platform is rotated in relation to the opticalunit at set angular variations. The magnitude of the angular variationsdetermines the extent of data collection; for example, how many imageswill be collection of the gemstone. For example, if the platform isrotated at an angular variation of 12 degree, a full rotation will allow30 images of the gemstone to be collected. The angular variation can beset at any value to facilitate data collection and analysis. Forexample, the platform can be rotated at an angular variation of 0.5degree or smaller, 1 degree or smaller, 1.5 degree or smaller, 2 degreeor smaller, 3 degree or smaller, 4 degree or smaller, 5 degree orsmaller, 6 degree or smaller, 7 degree or smaller, 8 degree or smaller,9 degree or smaller, 10 degree or smaller, 12 degree or smaller, 15degree or smaller, 18 degree or smaller, 20 degree or smaller, 24 degreeor smaller, 30 degree or smaller, 45 degree or smaller, 60 degree orsmaller, 90 degree or smaller, 120 degree or smaller, 150 degree orsmaller, or 180 degree or smaller. It will be understood that theangular rotational variation can be set at any number. It will also beunderstood that the platform can be rotated for a total rotational angleof any value, not limited to a 360 degree full rotation. In someembodiments, data (e.g., color images) are collection for a rotationless than a 360 degree full rotation. In some embodiments, data (e.g.,color images) are collection for a rotation more than a 360 degree fullrotation.

In some embodiments, the platform or a portion thereof (e.g., the topsurface) is coated with a reflective surface to achieve reflectivity. Insome embodiments, the platform or a portion thereof (e.g., the topsurface) comprises a reflective material. In some embodiments, theplatform or a portion thereof (e.g., the top surface) is made of areflective material. In some embodiments, the reflective material is awhite reflective material. In some embodiments, the reflective materialis Teflon™ material. In some embodiments, the reflective materialincludes but is not limited to polytetrafluoroethylene (PTFE),Spectralon™, barium sulfate, Gold, Magnesium Oxide, or combinationsthereof.

Preferably, the rotatable platform is round and larger than the size ofany sample gemstone to be analyzed. In some embodiments, the platform ishorizontal and remains horizontal while it is being rotated.

In some embodiments, the height of the platform is fixed. In someembodiments, the height of the platform is adjusted, either manually orvia the control of a computer program. Preferably, the platform can beraised or lowered by via the control of a computer program run by thecomputer unit.

In some embodiments, the platform is flat. In some embodiments, thecenter area on which the gemstone sample is positioned is flat and themore peripheral area on the platform is not flat. The entire platformadopts the confirmation of a flatted dome-like structure.

In some embodiments, the relative position between the platform and theillumination source can be adjusted. For example, the illuminationsource can be moved closer or further away from the platform.

A platform can be made of any rigid and non-transparent material such asmetal, wood, dark glass, plastic or other rigid polymeric material. Insome embodiments, the platform and/or area surrounding the platform arecoated with non-reflective or low-reflective material.

In the broadest sense, a light source 20 includes but is not limited tothe source for generating light, one or more filters, elements forconducting the generated light, and a component (e.g., a circular ringlight) that emit the generated light as UV illumination. In theembodiment depicted in FIG. 3, a circular ring light 530 provides UVillumination to the sample gemstone. As disclosed herein, the source forgenerating light is sometimes referred to as light source. One of skillin the art would understand that the illumination component is also apart of the light source.

In some embodiments, the light generating source is separated from theultimate illumination component, for example, it is connected with anexternal circular ring light (e.g., by light transmission cables) toprovide the source of illumination. In such embodiments, a short-passfilter and band-pass filter for UV light selection is applied, eitherbefore or after the source of illumination reaches the circular ringlight. As such, illumination ultimately provided the circular ring lighthas a defined ultraviolet feature; for example, having one or morewavelengths within the UV range. Such wavelengths can be any wavelengthfrom a range of 400 nm to 10 nm, 400 nm to 385 nm, 385 nm to 350 nm, 350nm to 300 nm, 300 nm to 250 nm, 250 nm to 200 nm, 200 nm to 150 nm, 150nm to 100 nm, 100 nm to 50 nm, or 50 nm to 10 nm.

In one aspect, a light generating source as disclosed herein is capableof generating fluorescence excitation (e.g., at 365 nm). In anotheraspect, a light generating source as disclosed herein provides lightillumination for gemstone outline identification. Thisdual-functionality is achieved by using special light source andcombination of different types of light source.

In some embodiments, a tunable light source that is capable of emittingboth UV and white light is used. For example, such tunable light sourcecomprises one or more LEDs. Advantageously, such light source can beused for both outline identification and fluorescence measurements. Forexample, a built-in mechanism can be used to allow a user to switchbetween two modes of operation. In some embodiments, the light source(e.g., UV emitting LEDs) emits UV illumination at a desired wavelength(e.g., at 365 nm). For example, UV LEDs that emit UV light at a singlewavelength (e.g., 365 nm or 385 nm) are available (e.g., from HamamatsuCorporation). In some embodiments, the light source (e.g., UV emittingLEDs) emits UV illumination at a range and a desired wavelength isemitted by applying a UV-pass filter set, for example, at 365 nm.

In such embodiments, the tunable light source provides either uniformtop illumination or uniform bottom illumination. For top illumination,there are no limitations on the shape and size of the light source. Forexample, the light source can be circular, partially circular, ornon-circular at all (e.g., oval, square or triangle). There are also nolimitations on the distance from the gemstone sample. For example, thetunable light source is attached to the reflective internal surface oftop reflect element 60 (e.g., FIG. 2B). A combination of light sourcescan be used; including but not limited to one or more UV LEDs; one ormore UV LEDs with an optical diffuser; one or more UV LEDs with acollimation lens; or one or more UV LEDs with a collimation lens and anoptical diffuser. One of skill in the art would understand that anycombination of light source and optical elements that can provideuniform illumination will be suitable as light source in an apparatus asdisclosed herein.

For bottom illumination, the light source is preferably a circular ringlight to be compatible with the shape of sample platform 50 (e.g., FIG.2B). Here, elements that can generate UV illumination is arranged into acircular or near circular shape. For example, UV LEDs that emit UV lightat a single wavelength (e.g., 365 nm or 385 nm) are available (e.g.,from Hamamatsu Corporation). In some embodiments, the ring light hasembedded within one or more UV LEDs.

In some embodiments, more than one light sources are used. At least oneof the light sources is a UV light source (such as one or more UVemitting LEDs). At least another one of the light sources is a whitelight source. Any suitable white light source can be used, including butnot limited to a fluorescence lamp, a halogen lamp, a Xe lamp, aTungsten lamp, a metal halide lamp, a laser-induced white light (LDLS),or combinations thereof.

Many combinations can be used in such embodiments. For example, two ringlights can be used: one providing uniform UV illumination and oneproviding uniform daylight approximating light illumination. In thiscombination, in some embodiments, the light sources both provide bottomillumination. In some embodiments, one of the ring light provides bottomillumination while the other provides top illumination.

In another exemplary combination, the light source comprises aring-shaped LED light source and a white light source. In someembodiments, the ring-shaped of UV LED is used to provide bottomillumination and the white light source provides top illumination.

In still another exemplary combination, the light source comprises aring-shaped white light source and an LED light source. In someembodiments, the ring-shaped white light source is used to providebottom illumination and the UV LED source provides top illumination.

As noted, the white light source comprises a daylight-approximatinglight source. Exemplary daylight-approximating light source includes butis not limited to one or more halogen lamps with a color balancingfilter, multiple light emitting diodes arranged in a ring-like structuresurrounding the platform surface, fluorescence lamp, Xe lamp, Tungstenlamp, metal halide lamp, laser-induced white light (LDLS), orcombinations thereof. In some embodiments, a color balancing filter isused to create the day-light equivalent light source.

In some embodiments, when suitable, either the white light source or theUV light source can be a ring-shaped light. For example, for a UV lightsource, elements that can generate UV illumination is arranged into acircular or near circular shape. For example, UV light emitting diodesthat emit UV light at a single wavelength (e.g., 365 nm or 385 nm) areavailable (e.g., from Hamamatsu Corporation). In some embodiments, thering light has embedded within one or more UV LEDs.

In some embodiments, cables such as gooseneck light guide, flexiblelight guide, each containing one or more branches are used to connectedthe ring light with the light generating source.

The UV illumination source can adopt any shape and size that aresuitable for the optical analysis of a sample gemstone. For example, theillumination source can be a point light, a round light, a ring light,an oval light, a triangular light, a square light, or any other lightwith suitable size and shape. In some embodiments, the lightilluminating source is ring-like or circular in shape, with a diameterthat is larger than that of a circular platform.

The UV illumination component provides the input light under which thesample gemstone can be analyzed. Advantageously, in an environment withno or little light interference (e.g., from the ambient light or otherlight), a gemstone that can generate fluorescence under UV illuminationcan be analyzed with great sensitivity. Here, visible fluorescence isemitted as a result of exposure to UV illumination. When the impact fromUV illumination is excluded (e.g., for setting the light filter on adetector or image capture component to only visible light range), theemitted fluorescence light is compared against a zero background (e.g.,no fluorescence). Here, the signal to noise ratio is very high due tothe low or near zero noise level.

A modular approach to the design of the apparatus has been adopted toprovide experimental flexibility. In some embodiments, the intensity ofthe UV illumination can be adjusted to optimize image collection.

A modular approach to the design of the apparatus has been adopted toprovide experimental flexibility. In some embodiments, the intensity ofthe UV illumination can be adjusted to optimize image collection.

As shown in FIGS. 2A and 2B, a top reflector module can be moved overthe area where a sample gemstone is position. In the closedconfiguration shown in FIG. 2A, the internal cavity of the top reflectormodule functions as a sealed and isolated sample chamber in which thesample gemstone is analyzed in a controlled environment. For example,ambient light or other light is excluded from the chamber. A user canadjust light intensity within the chamber to optimize data collection.In some embodiments, data collected include color images of the gemstoneviewed from different angles.

FIGS. 5A through 5D illustrate an exemplary embodiment of the topreflector component 60. Overall, the top reflector has an externalmorphology that resembles that of a short cylinder, except that aportion of the cylinder is carved away to form a curved slope (see, forexample, element 610 in FIGS. 5B and 5D). A portion of the slope isremoved to allow access to the inside of the reflector component. Forexample, as shown in FIGS. 5A-5D, the lower portion of slope 610 isremoved to form an opening 620. In some embodiments, the top port ofopening 620 is circular in design; for example with a diameter throughwhich a lens from the optical unit is fitted. In some embodiments, thediameter is the same as that of the telecentric lens to prevent ambientlight or other light from entering the inside of the reflector. In someembodiments, the diameter is slightly larger than that of thetelecentric lens such that an adaptor module is needed to preventambient light or other light from entering the inside of the reflector.

Inside of top reflector module 60 is reflective surface 630. Thisinternal reflective surface is at least partially hemispherical. In someembodiments, the internal reflective surface adopts a shape that is partof the involute of a circle having a radius R. In preferred embodiments,the circle is located at the center of the platform surface and has adiameter that is larger than the sizes of the gemstones being analyzed.The shape of the involute surface is described based on the followingequations:

x=R(cos θ+θ sin θ)

y=R(sin θ−θ cos θ),

where R is the radius of the circle and θ is an angle parameter inradians. The involute surface will reflect light toward the centercircular region such that illumination of the gemstone being analyzed isoptimized.

In some embodiments, the reflective surface 630 or a portion thereofcomprises a reflective material. In some embodiments, the reflectivesurface 630 or a portion thereof is made of a reflective material. Insome embodiments, the reflective material is a white reflectivematerial. In some embodiments, the reflective material is Teflon™material. In some embodiments, the reflective material includes but isnot limited to polytetrafluoroethylene (PTFE), Spectralon™, bariumsulfate, Gold, Magnesium Oxide, or combinations thereof. Additionalreflective coating materials include but are not limited to a zinc salt(zinc sulfide), titanium dioxide, silicon dioxide, a magnesium salt(magnesium fluoride, magnesium sulfide).

In some embodiments with bottom UV illumination (e.g., when a ring lightof UV LEDs are used), one or more reflective materials are used toreflect UV illumination towards the gemstone. In some embodiments withtop UV illumination, reflective material is not needed.

As illustrated in FIG. 2B, an optical connector module 70 links thegemstone evaluation unit with the optical unit to permit data collectionby image capturing device 40, whiling at the same time preventingambient light or other light from entering the gemstone evaluation unitand interfering with data measurements.

FIGS. 6A to 6C provide more detailed illustrations of an exemplaryembodiment of an optical connector module. In this case, the connectoris a lens hood for receiving the telecentric lens 30. On the side incontact with the telecentric lens, the lens hood has a flat surface 710.On the opposite side which contacts the reflector, the lens hood has acurved surface 720. In some embodiments, the curved surface 720 has ashape complementary to the curved surface 610 on the reflector.

Additionally, the connector also has an opening 730; see, FIGS. 6A, 6B,and 6C. In some embodiments, opening 730 has a configuration thataccommodates the telecentric lens while preventing interference fromambient light or other light. For example, opening 730 depicted in FIGS.6A-6B has a cylindrical opening that is not uniform in size. Forexample, the diameter of the cylindrical opening on the lens-contactingside is smaller than the diameter of the cylindrical opening on thereflector-contacting side.

A lens hood or other optical connector module allows integration of twodifferent functional components. It is designed such that no or verylittle ambient light or other light enters the sample chamber. In someembodiments, additional elements such as a sealing tape can be used toexclude ambient light or other light.

Another main functional component of the system is an optical unitthrough which data of the gemstones being analyzed. The optical unitprovides a sample chamber that enables the collection of a visible-lightspectrum from an area containing a sample gemstone while excluding lightfrom outside the chamber. Optical measurement such as an image iscaptured of the area containing the sample gemstone and, possiblythrough analysis of the detailed structure of the images, to providesome insight into the reasons for certain stones that previously hadanomalous grading results.

Exemplary embodiments disclosed herein include but are not limited totwo important functional modules in the optical unit a telecentric lens30 and an image capturing component 40 such as a color camera. One ofskill in the art would understand that additional components can bepresent to facilitate data collection.

A telecentric lens is used to provide an image of the illuminatedgemstone to the image capturing component. Telecentricity refers to aunique optical property where the chief rays (oblique rays which passthrough the center of the aperture stop) through a certain lens designare collimated and parallel to the optical axis in image and/or objectspace. A telecentric lens is a compound lens which has its entrance orexit pupil at infinity. Advantageously, a telecentric lens providesconstant magnification (object size does not change) over a range ofworking distances, virtually eliminating perspective angle error. Formany applications, this means that object movement does not affect imagemagnification, allowing for highly accurate measurements in gaugingapplications. This level of accuracy and repeatability cannot beobtained with standard lenses. The simplest way to make a lenstelecentric is to put the aperture stop at one of the lens's focalpoints.

There are three types of telecentric lens. An entrance pupil at infinitymakes a lens object-space telecentric. An exit pupil at infinity makesthe lens image-space telecentric. If both pupils are at infinity, thelens is double telecentric.

Telecentric lens with high depth of field are used in the systemdisclosed herein. In some embodiments, a telecentric lens used is anobject-space telecentric lens. In some embodiments, a telecentric lensis a double telecentric lens. In preferred embodiments, zoom should befixed for all images collection for a given gemstone stone to furtherensure consistency.

Advantageously, the present apparatus and system do not require that thesample gemstone be placed at the center of the platform surface. Inaddition, a telecentric lens does not discriminate the size of thesample gemstones. The same telecentric lens can be used to collectionimages for a very small gemstone and a significantly larger gemstone.

The optical unit further comprises an image capture component or adetector such as a digital camera. In order to only capture fluorescenceemitted from the gemstones, a filter is applied to exclude interferencefrom UV illumination.

In some embodiments, image capturing component 40 comprises one or morephotodiode arrays of a CCD (charge coupled device). In some embodiments,image capturing component 40 comprises one or more CMOS (complementarymetal oxide semiconductor) image sensors. In some embodiments, imagecapturing component 40 comprises a combination of one or more photodiodearrays with CMOS sensors. In some embodiments, image capturing component40 is a CCD digital camera, such as a color digital camera. When imagesfrom different fluorescence grading apparatuses are analyzed, moreconsistent results can be obtained if the apparatuses use the same typeof detection methods; for example, all CCD arrays, all CMOS sensors, orthe same combination of both types.

For more accurate analytical results, the resolution limit for thedigital images collected is 600 pixel×400 pixel or above. In someembodiments, each pixel has an 8-bit value (e.g., 0 to 255) for eachcolor component. The Analog to Digital Converter (ADC) of the digitalcamera is 8-bit or above in order to efficiently process the informationembedded in the pixels without little or no loss of image quality. Insome embodiments, the ADC is 10-bit or above according to the dynamicrange of image capturing component. In some embodiments, the ADC isbetween 10-bit and 14-bit.

In some embodiments, the color components in a pixel include but notlimited to red (R), green (G) and blue (B). In some embodiments, thecolor components in a pixel include but not limited to) cyan (C),magenta (M), yellow (Y), and key (black or B). In some embodiments, thecolor components in a pixel include but not limited to red (R), yellow(Y) and blue (B).

Image View Angle:

As depicted in FIG. 4, an image capturing device the optical unit (ortelecentric lens 30 or both) is positioned at a pre-determined angle(alpha, also referred to as the image view angle) relative to theplatform surface. In some embodiments, the image view angle is 65 degreeor smaller, 60 degree or smaller, 56 degree or smaller, 52 degree orsmaller, 50 degree or smaller, 48 degree or smaller, 46 degree orsmaller, 44 degree or smaller, 42 degree or smaller, 40 degree orsmaller, 39 degree or smaller, 38 degree or smaller, 37 degree orsmaller, 36 degree or smaller, 35 degree or smaller, 34 degree orsmaller, 33 degree or smaller, 32 degree or smaller, 31 degree orsmaller, 30 degree or smaller, 29 degree or smaller, 28 degree orsmaller, 27 degree or smaller, 26 degree or smaller, 25 degree orsmaller, 24 degree or smaller, 23 degree or smaller, 22 degree orsmaller, 21 degree or smaller, 20 degree or smaller, 19 degree orsmaller, 18 degree or smaller, 17 degree or smaller, 16 degree orsmaller, 15 degree or smaller, 14 degree or smaller, 13 degree orsmaller, 12 degree or smaller, 11 degree or smaller, or 10 degree orsmaller. In some embodiments, the image view angle is between about 10degree and about 45 degree. For consistency, the image view angle for agiven gemstone will remain constant when images are collected.

Image Rotational Angle:

Also as illustrated in FIG. 4, the relative rotational position betweenthe imaging capturing component and a pre-defined location on theplatform (e.g., point 540) can be described by an image rotational anglebeta. For example, the image capturing component and the platformsurface can be rotated relative to each other such that the imagerotational angle is varied by a set angular variation betweenconsecutive images. For example, the angular variation between twoconsecutive images can be 0.5 degree or smaller, 1 degree or smaller,1.5 degree or smaller, 2 degree or smaller, 3 degree or smaller, 4degree or smaller, 5 degree or smaller, 6 degree or smaller, 7 degree orsmaller, 8 degree or smaller, 9 degree or smaller, 10 degree or smaller,12 degree or smaller, 15 degree or smaller, 18 degree or smaller, 20degree or smaller, 24 degree or smaller, 30 degree or smaller, 45 degreeor smaller, 60 degree or smaller, 90 degree or smaller, or 180 degree orsmaller. It will be understood that the angular rotational variation canbe set at any number.

It will also be understood that the platform and image capturingcomponent can be rotated relative to each other for a total rotationalangle of any value, not limited to a 360 degree full rotation. In someembodiments, data (e.g., color images) are collection for a rotationless than a 360 degree full rotation. In some embodiments, data (e.g.,color images) are collection for a rotation more than a 360 degree fullrotation.

It is possible to change angular rotational variation when collecting aset of images for the same sample gemstone. For example, the angulardifferent between image 1 and image 2 can be 5 degrees, but thedifferent between image 2 and 3 can be 10 degrees. In preferredembodiments, angular difference between consecutive images remainsconstant within the same set of images for the same sample gemstone. Insome embodiments, only one set of images is collection for a givensample gemstone. In some embodiments, multiple sets of images arecollected for the same gemstone where angular differences remainconstant within each set but are different from each other. For example,a first set of images is collected by varying the rational image angleby 12 degree for consecutive images, while a second set of images iscollected by varying the rational image angle by 18 degree forconsecutive images.

The number of images collected for a given sample gemstone variesdepending on the characteristics of the gemstone. Exemplarycharacteristics include but are not limited to shape, cut, size, colorand etc.

Visible-light spectra from an area on the platform surface that containsthe sample gemstone is selectively collected. In some embodiments,multiple color images are collected for each gemstone. In someembodiments, multiple non-color images are collected for each gemstone.Color images are advantageous for determining, for example, the colorgrade of a cut diamond.

In some embodiments, as will be discussed further in sections thatfollow, images captures by the CCD camera will be processed in order toidentify regions of differing intensity of color or fluorescence.Furthermore, colorimetric calculations can be performed on thesedifferent areas using the red, green and blue signals from the camerapixels. In some embodiment, such calculations will be sufficientlyaccurate to give a fluorescence grade. In some embodiment, suchcalculations will be sufficiently accurate to provide a colordistribution across the diamond and the comparison of these colorcalculations with that obtained from the measured spectrum can helpidentify diamonds that are likely to give anomalous results.

In some embodiments, the fluorescence grade is determined based on colorvalues computed from the entire sample gemstone. In some embodiments,the fluorescence grade is determined based on color values computed fromcolor area of the sample gemstone.

Resolution and capacity of a detector can be determined by the numberand size of the pixel in the detector arrays. In general, the spatialresolution of the digital image is limited by the pixel size.Unfortunately while reducing pixel size improves spatial resolution thiscomes at the expense of signal to noise ratio (SNR or signal/noiseratio). In particular, signal-to-noise ratio is improved when imagesensor pixel size is increased or image sensor is cooled. At the sametime, size of the image sensor is increased if image sensor resolutionis kept the same. Detectors of higher quality (e.g., better digitalcameras) have a large image sensor and a relatively large pixel size forgood image quality.

In some embodiments, a detector of the present invention has a pixelsize of 1 μm2 or smaller; 2 μm2 or smaller; 3 μm2 or smaller; 4 μm2 orsmaller; 5 μm2 or smaller; 6 μm2 or smaller; 7 μm2 or smaller; 8 μm2 orsmaller; 9 μm2 or smaller; 10 μm2 or smaller; 20 μm2 or smaller; 30 μm2or smaller; 40 μm2 or smaller; 50 μm2 or smaller; 60 μm2 or smaller; 70μm2 or smaller; 80 μm2 or smaller; 90 μm2 or smaller; 100 μm2 orsmaller; 200 μm2 or smaller; 300 μm2 or smaller; 400 μm2 or smaller; 500μm2 or smaller; 600 μm2 or smaller; 700 μm2 or smaller; 800 μm2 orsmaller; 900 μm2 or smaller; 1,000 μm2 or smaller; 1,100 μm2 or smaller;1,200 μm2 or smaller; 1,300 μm2 or smaller; 1,400 μm2 or smaller; 1,500μm2 or smaller; 1,600 μm2 or smaller; 1,700 μm2 or smaller; 1,800 μm2 orsmaller; 1,900 μm2 or smaller; 2,000 μm2 or smaller; 2,100 μm2 orsmaller; 2,200 μm2 or smaller; 2,300 μm2 or smaller; 2,400 μm2 orsmaller; 2,500 μm2 or smaller; 2,600 μm2 or smaller; 2,700 μm2 orsmaller; 2,800 μm2 or smaller; 2,900 μm2 or smaller; 3,000 μm2 orsmaller; 3,100 μm2 or smaller; 3,200 μm2 or smaller; 3,300 μm2 orsmaller; 3,400 μm2 or smaller; 3,500 μm2 or smaller; 3,600 μm2 orsmaller; 3,700 μm2 or smaller; 3,800 μm2 or smaller; 3,900 μm2 orsmaller; 4,000 μm2 or smaller; 4,100 μm2 or smaller; 4,200 μm2 orsmaller; 4,300 μm2 or smaller; 4,400 μm2 or smaller; 4,500 μm2 orsmaller; 4,600 μm2 or smaller; 4,700 μm2 or smaller; 4,800 μm2 orsmaller; 4,900 μm2 or smaller; 5,000 μm2 or smaller; 5,100 μm2 orsmaller; 5,200 μm2 or smaller; 5,300 μm2 or smaller; 5,400 μm2 orsmaller; 5,500 μm2 or smaller; 5,600 μm2 or smaller; 5,700 μm2 orsmaller; 5,800 μm2 or smaller; 5,900 μm2 or smaller; 6,000 μm2 orsmaller; 6,500 μm2 or smaller; 7,000 μm2 or smaller; 7,500 μm2 orsmaller; 8,000 μm2 or smaller; 8,500 μm2 or smaller; 9,000 μm2 orsmaller; or 10,000 μm2 or smaller. In some embodiments, the pixel sizeis larger than 10,000 μm2; for example, up to 20,000 μm2; 50,000 μm2; or100,000 μm2.

In some embodiments, exposure time to the detector can be adjusted tooptimize image quality and to facilitate the determination of a gradefor an optical quality of the gemstone, such as color or fluorescencelevel. In some embodiments, fluorescence emission is quite weak andconsequently long exposure time is needed for assessing fluorescencequality. For example, the exposure time to a CCD detector can be 0.1millisecond (ms) or longer, 0.2 ms or longer, 0.5 ms or longer, 0.8 msor longer, 1.0 ms or longer, 1.5 ms or longer, 2.0 ms or longer, 2.5 msor longer, 3.0 ms or longer, 3.5 ms or longer, 4.0 ms or longer, 4.5 msor longer, 5.0 ms or longer, 5.5 ms or longer, 6.0 ms or longer, 6.5 msor longer, 7.0 ms or longer, 7.5 ms or longer, 8.0 ms or longer, 8.5 msor longer, 9.0 ms or longer, 9.5 ms or longer, 10.0 ms or longer, 15.0ms or longer, 20.0 ms or longer, 25.0 ms or longer, 30.0 ms or longer,35.0 ms or longer, 40.0 ms or longer, 45.0 ms or longer, 50.0 ms orlonger, 55.0 ms or longer, 60.0 ms or longer, 65.0 ms or longer, 70.0 msor longer, 75.0 ms or longer, 80.0 ms or longer, 85.0 ms or longer, 90.0ms or longer, 95.0 ms or longer, 100.0 ms or longer, 105.0 ms or longer,110.0 ms or longer, 115.0 ms or longer, 120.0 ms or longer, 125.0 ms orlonger, 130.0 ms or longer, 135.0 ms or longer, 140.0 ms or longer,145.0 ms or longer, 150.0 ms or longer, 175.0 ms or longer, 200.0 ms orlonger, 225.0 ms or longer, 250.0 ms or longer, 275.0 ms or longer,300.0 ms or longer, 325.0 ms or longer, 350.0 ms or longer, 375.0 ms orlonger, 400.0 ms or longer, 425.0 ms or longer, 450.0 ms or longer,475.0 ms or longer, 500.0 ms or longer, 550.0 ms or longer, 600.0 ms orlonger, 650.0 ms or longer, 700.0 ms or longer, 750.0 ms or longer,800.0 ms or longer, 850.0 ms or longer, 900.0 ms or longer, 950.0 ms orlonger, 1 s (second) or longer, 1.1 s or longer, 1.2 s or longer, 1.3 sor longer, 1.4 s or longer, 1.4 s or longer, 1.5 s or longer, 1.6 s orlonger, 1.7 s or longer, 1.8 s or longer, 1.9 s or longer, 2 s orlonger, 2.5 s or longer, 3 s or longer. It is understood that the timeof exposure can vary with respect to, for example, light sourceintensity.

In another aspect, the methods and systems disclosed herein are used todetect or evaluate changes of fluorescence properties of a samplegemstone over time. For example, the color of the fluorescence of agemstone may change over time. Also, the intensity of the fluorescenceof a gemstone may change over time.

In such embodiments, multiple sets or pluralities of images (e.g., colorimages) are collected of a gemstone over a period of time. For example,using the system disclosed herein, each set of image is collectedautomatically over multiple image angles. There is no limitation as tohow much sets of image can be collected over time, for example, two ormore sets of images; three or more sets of images; four or more sets ofimages; five or more sets of images; six or more sets of images; sevenor more sets of images; eight or more sets of images; nine or more setsof images; 10 or more sets of images; 15 or more sets of images; 20 ormore sets of images; 30 or more sets of images; 50 or more sets ofimages; or 100 or more sets of images can be collected.

In some embodiments, all sets of images are collected of the samegemstone by applying the same system configuration; for example, usingthe same camera, same image angle, same reflector, same platform andetc.

Among the multiple sets of images, two consecutive sets of image areseparately for a time gap ranging from minutes to hours or even days,depending on the nature of the color change of the stone. The durationof the time gap is determined by how quickly color changes may takeplace in the sample stone. There is no limitation as to how long or howshort the time gap can be. For example, the time gap can be two minutesor shorter; five minutes or shorter; 10 minutes or shorter; 20 minutesor shorter; 30 minutes or shorter; 60 minutes or shorter; 2 hours orshorter; 5 hours or shorter; 12 hours or shorter; 24 hours or shorter; 2days or shorter; 5 days or shorter; or 10 days or shorter.

In some embodiments, calculations are done for each set of images toassign a fluorescence grade for the sample gemstone. Fluorescence gradesfrom multiple sets of images are then compared to determine fluorescencechange over time.

In another aspect, also provided herein is a data analysis unit,including both a hardware component (e.g., computer) and a softwarecomponent.

The data analysis unit stores, converts, analyzes, and processes of theimages collected by the optical unit. The computer unit controls variouscomponents of the system, for example, rotation and height adjustment ofthe platform, adjustment of the intensity and exposure time of theillumination source. The computer unit also controls the zoom, adjustsrelative position of the optic unit to the gemstone platform,

FIG. 8 illustrates an exemplary computer unit 800. In some embodiments,a computer unit 800 comprises a central processing unit 810, a powersource 812, a user interface 820, communications circuitry 816, a bus814, a non-volatile storage controller 826, an optional non-volatilestorage 828, and a memory 830.

Memory 830 may comprise volatile and non-volatile storage units, forexample random-access memory (RAM), read-only memory (ROM), flash memoryand the like. In some embodiments, memory 830 comprises high-speed RAMfor storing system control programs, data, and application programs,e.g., programs and data loaded from non-volatile storage 828. It will beappreciated that at any given time, all or a portion of any of themodules or data structures in memory 830 can, in fact, be stored inmemory 828.

User interface 820 may comprise one or more input devices 824, e.g.,keyboard, key pad, mouse, scroll wheel, and the like, and a display 822or other output device. A network interface card or other communicationcircuitry 816 may provide for connection to any wired or wirelesscommunications network. Internal bus 814 provides for interconnection ofthe aforementioned elements of the computer unit 30.

In some embodiments, operation of computer unit 800 is controlledprimarily by operating system 828, which is executed by centralprocessing unit 810. Operating system 382 can be stored in system memory830. In addition to operating system 382, a typical implementation ofsystem memory 830 may include a file system 834 for controlling accessto the various files and data structures used by the present invention,one or more application modules 836, and one or more databases or datamodules 852.

In some embodiments in accordance with the present invention,applications modules 836 may comprise one or more of the followingmodules described below and illustrated in FIG. 8.

Data Processing Application 838:

In some embodiments in accordance with the present invention, a dataprocessing application 838 receives and processes optical measurementsshared between the optical unit and data analysis unit. In someembodiments, data processing application 838 utilizes an algorithm todetermine the portion of the image that corresponds to the samplegemstone and eliminates the irrelevant digital data. In someembodiments, data processing application 838 converts each pixel of thedigital images into individual color components.

Content Management Tools 840:

In some embodiments, content management tools 840 are used to organizedifferent forms of data 852 into multiple databases 854, e.g., an imagedatabase 856, a processed image database 858, a reference gemstonedatabase 860, and an optional user password database 862. In someembodiments in accordance with the present invention, content managementtools 840 are used to search and compare any of the databases hosted oncomputer unit 30. For example, images of the same sample gemstone takenat different time can be organized into the same database. In addition,information concerning the sample gemstone can be used to organize theimage data. For example, images of diamonds of the same cut may beorganized into the same database. In addition, images of diamonds of thesame source may be organized into the same database.

The databases stored on the computer unit 800 comprise any form of datastorage system including, but not limited to, a flat file, a relationaldatabase (SQL), and an on-line analytical processing (OLAP) database(MDX and/or variants thereof). In some specific embodiments, thedatabases are hierarchical OLAP cubes. In some embodiments, thedatabases each have a star schema that is not stored as a cube but hasdimension tables that define hierarchy. Still further, in someembodiments, the databases have hierarchy that is not explicitly brokenout in the underlying database or database schema (e.g., dimensiontables are not hierarchically arranged).

In some embodiments, content management tools 840 utilize a clusteringmethod for determining grading characteristics.

System Administration and Monitoring Tools 842:

In some embodiments in accordance with the present invention, the systemadministration and monitoring tools 842 administer and monitor allapplications and data files of computer unit 30. System administrationand monitoring tools 842 control which users, servers, or devices haveaccess to computer unit 30. In some embodiments, security administrationand monitoring is achieved by restricting data download or upload accessfrom computer unit 800 such that the data is protected against maliciousaccess. In some embodiments, system administration and monitoring tools842 use more than one security measure to protect the data stored oncomputer unit 30. In some embodiments, a random rotational securitysystem may be applied to safeguard the data stored on remote computerunit 30.

Network Application 846:

In some embodiments, network applications 846 connect computer unit 800to network and thereby to any network devices. In some embodiments, anetwork application 846 receives data from intermediary gateway serversor one or more remote data servers before it transfers the data to otherapplication modules such as data processing application 838, contentmanagement tools 840, and system administration and monitoring tools842.

Computational and Analytical Tools 848:

Computational and analytical tools 848 can apply any available methodsor algorithm to analyze and process images collected from a samplegemstone.

System Adjustment Tools 850:

System adjustment tools 850 controls and modifies configurations ofvarious components of the system. For example, system adjustment tools850 can switch between different masks, alter the size and shape of anadjustable mask, adjust zoom optics, set and modify exposure time, andetc.

Data Module 852 and Databases 854:

In some embodiments, each of the data structures stored on computer unit800 is a single data structure. In other embodiments, any or all suchdata structures may comprise a plurality of data structures (e.g.,databases, files, and archives) that may or may not all be stored oncomputer unit 30. The one or more data modules 852 may include anynumber of databases 852 organized into different structures (or otherforms of data structures) by content management tools 840.

In addition to the above-identified modules, various database 854 may bestored on computer unit 800 or a remote data server that is addressableby computer unit 800 (e.g., any remote data server that the computerunit can send information to and/or retrieve information from).Exemplary databases 854 include but are not limited to image database856, processed image database 858, reference gemstone database 860,optional member password dataset 862, and gemstone data 864.

Image database 856 is used to store images of gemstones before they areanalyzed. Processed image database 858 is used to store processedgemstone images. In some embodiments, processed image database 858 alsostored data that are converted from processed images. Examples ofconverted data include but are not limited to individual colorcomponents of pixels in an image, a two or three dimensional maprepresenting color distribution of the pixels in an image; computed L*,C*, a or b values of pixels in an image; average of L*, C*, a or bvalues for one or more images.

Reference Gemstone Database 860:

Data of existing or known reference, or master gemstones (e.g., gradevalues or L*, C*, a or b values) are stored in reference gemstonedatabase 860. In some embodiments, information of the known reference,or master gemstones is used as standards for determining the gradevalues, or L*, C*, a or b values of an unknown gemstone samples. Theoptical quality, such as color or fluorescence grade, has already beendetermined for the known reference, or master gemstones. For example,optical measurements of a sample diamond of brilliant cut are used tocompute a value of L*, C*, a or b, which is then compared with thevalues of L*, C*, a or b of a plurality of known reference, or masterdiamond of the same cut. The grade of the sample diamond will bedetermined by the most closely match reference gemstone. In preferredembodiments, the reference gemstones are of the same or similar size orweight as the sample gemstone.

Optional User Password Database 862:

In some embodiments, an optional password database 862 is provided.Password and other security information relating to users of the presentsystem can be created and stored on computer unit 800 where passwords ofthe users are stored and managed. In some embodiments, users are giventhe opportunity to choose security settings.

In one aspect, provided herein are methods for system calibration, datacollection, data processing and analysis. For example, color digitalimages of gemstones are obtained, processed and computed to render oneor more values for assessing and grading quality of cut gemstones suchas diamonds.

Not all gemstones emit fluorescence upon UV exposure. Even for gemstonesthat do emit fluorescence upon UV exposure, fluorescence levels are veryunlikely to be uniform because fluorescent material within a gemstone isusually not uniformly distributed. Further, not all parts of a gemstonecan emit fluorescence. An important aspect of fluorescence grading is toprecisely identify regions within which fluorescence is emitted and tofocus data analysis within such regions to improve accuracy.

For fluorescence analysis, at least two sets of test data are used. Forexample, for a given sample gemstone under the same conditions (e.g., ata set image view angle and set image rotational angle), at least twoimages are captured: one image under regular non-UV illumination (e.g.,under a visible daylight approximating light source), and another imageunder UV illumination (e.g., a fluorescence or fluorescent image, alsoreferred to as a UV image). In some embodiments, the set of imagescaptured under regular non-UV illumination is used to extrapolateoutline masks. In some embodiments, the set of images captured under UVillumination is used to extrapolate area of fluorescence (e.g., FIGS. 7Cand 7D). In contrast, for color analysis, one set of test data is used.For example, a sample gemstone is under the same illumination conditions(e.g., under a daylight approximating light source) while multiple colorimages of the sample gemstone are captured with a telecentric lens atthe same image view angle while changing the image rotational angle at aset interval.

FIGS. 7A and 7B illustrate images of a diamond in which the backgroundwhite color has been masked to highlight the presence of the diamond. Asillustrated in FIG. 7B, the dark area surrounding the diamond forms anoutline mask. In some embodiments, an outline mask corresponds to thephysical boundaries or edges of a sample gemstone, as viewed at a givenimage view angle and a given image rotational angle. Consequently, theopening of the outline mask encompasses a full image or the entire areaof the sample gemstone at the given image view angle and imagerotational angle. As illustrated in the method of analysis section, suchoutline masks can be defined for each image to isolate the region ofanalysis and to extract measurements such as width and height.

FIG. 7C depicts a gemstone illuminated under a visible light source,before (a) and after (b) outline extraction. As illustrated, theresulting outline mask corresponds to the physical size of the diamondin two dimensions under the specific image capturing conditions. FIG. 7Ddepicts a gemstone illuminated under a UV light source in a fluorescenceimage, before (a) and after (b) fluorescence extraction. Here, it isimportant to understand that the area appearing to be fluorescent in afluorescence image (i.e., the apparent fluorescence area) can bedifferent in size (e.g., larger) than the area (or areas) within agemstone that is capable of emitting fluorescence, because fluorescenceemission when captured in an image can extend from the area emittingfluorescence. As shown in (b), the apparent fluorescence area is in factlarger than the physical size of the diamond itself due to fluorescentlight being reflected from a sample platform. As a result, the apparentfluorescence area is much larger than the opening of the outline mask,as illustrated in the comparison between FIG. 7C(b) and FIG. 7D(b). Insome embodiments, the outline mask is used to calculate fluorescenceintensity; for example, as represented by the parameter L according toCommission Internationale de l'Eclairage (CIE or the InternationalCommission on Illumination). Here, the entire area of the gemstone willbe assessed to accurately quantitate the overall fluorescence emissionlevel of the gemstone.

A fluorescence mask is used to define the area within the gemstone thatwill be subject to further analysis or calculation. In the scenarioillustrated in FIGS. 7C and 7D, the apparent fluorescence area is muchlarger than the physical size of the gemstone (e.g., as represented bythe opening of an outline mask), which suggests that the apparentfluorescence area includes areas that do not correspond to any part of agemstone. To eliminate inaccuracies, any fluorescence beyond thephysical boundaries of the gemstone is removed from further dataanalysis. Only fluorescent measurements from within the boundaries of agemstone will be subject to further calculation and analysis to provideassessment of the fluorescence light emitted from the gemstone. Whenfluorescence is emitted from the entire gemstone and the apparentfluorescence area covers the entire gemstone, the fluorescence mask isidentified by overlaying the apparent fluorescence area; e.g., FIG.7D(b), onto the outline mask for the gemstone; e.g., FIG. 7C(b). Anyarea in the apparent fluorescence area that is outside of the boundariesdefined by the outline mask will be eliminated. The remaining portion ofthe apparent fluorescence area corresponds to the fluorescence mask. Infact, fluorescence mask is calculated by FIG. 7C (b)×FIG. 7D (b). Couldyou change the above description accordingly? Under the abovedescription, inhomogeneous strong fluorescence diamond cannot becovered.

In other gemstones, an apparent fluorescence area can also be smallerthan the physical boundaries of the gemstone, as defined by an outlinemask and shown in FIGS. 7E and 7F. FIG. 7E illustrates an outlineextraction from (a) to (b), similar to that of FIG. 7C. In FIG. 7F,fluorescence is emitted from only limited areas within the gemstone. Theareas are small and disconnected. After fluorescence extraction isapplied, an apparent fluorescence area is obtained as indicated in FIG.7F(b). In this case, the apparent fluorescence area also containspatches of disconnected smaller areas. The overall apparent fluorescencearea is much smaller than the outline mask shown in FIG. 7E.

In the scenario illustrated in FIGS. 7E and 7F, the apparentfluorescence area is much smaller than the physical size of the gemstone(e.g., as represented by the opening of an outline mask). In addition,fluorescence in the apparent fluorescence area is non-contiguous, whichmeans that non-emitting areas have been excluded from the apparentfluorescence area. To eliminate inaccuracies, in some embodiments, afluorescence mask with an opening matching the smaller apparentfluorescence area will be used to define the area within the gemstonefor further analysis. Once again, the fluorescence mask is identified byoverlaying the apparent fluorescence area; e.g., FIG. 7F(b), onto theoutline mask for the gemstone; e.g., FIG. 7E(b). Any area in theapparent fluorescence area that is outside of the boundaries defined bythe outline mask will be eliminated. The remaining portion of theapparent fluorescence area corresponds to the fluorescence mask. Onlyfluorescent measurements from within the opening of the fluorescencemask will be subject to further calculation and analysis to provideassessment of the fluorescence light emitted from the gemstone.

In some embodiments, the fluorescence mask comprises a contiguousopening; see e.g., (b) of FIG. 7C. In some embodiments, the fluorescencemask comprises a non-contiguous opening; see, e.g., (b) FIG. 7F. In someembodiments, the total opening area of the fluorescence mask correspondsto the physical size of the gemstone. In some embodiments, the totalopening area of the fluorescence mask is much smaller than the physicalsize of the gemstone.

An exemplary process based on the apparatus and system disclosed hereinis outlined in FIG. 9A. One of skill in the art would understand thesteps provided are exemplary and can be applied in any order or used inany possible combination.

At step 9000, system calibration is performed. For example, in order tohave reproducible results and cancel out the fluctuation of non-UV lightsource, white balance of an image capture component such as a colorcamera is adjusted. At this step, the pixel gains of individual colorcomponents (e.g., RGB) are adjusted such that the background image ofthe platform surface becomes white. Background adjustment is done with abare platform surface; i.e., the sample gemstone is not yet positionedon the platform surface. Preferably, the background adjustment is doneafter the light source has stabilized. In some embodiments, thebackground adjustment is done with a short time period before images ofa sample gemstone are collected. In some embodiments, the backgroundadjustment is done after the light source has stabilized and soon beforegemstone image collection. White background adjustment is performed whenthe top reflector module 60 is in closed configuration. The topreflector module is then opened and a user can place a sample gemstoneat the center of the platform surface. Care is taken such that theplatform surface, illumination and other conditions and settings in thesample chamber and for the optical unit remain the same before and afterthe sample gemstone is placed.

Fluorescence measures the visible light emitted by fluorescent material(e.g., fluorophores) when it receive input energy from the UVillumination. It will be generally understood that the more intense theUV illumination, the more strongly the fluorescent material will emitvisible light.

In some embodiments, intensity of the input UV illumination is adjustedto optimize fluorescence measurements. For example, a power meter (e.g.,the PM160T thermal sensor power meter from Thorlabs) is used to measurelight intensity from the UV light source. UV intensity is adjusted tothe same intensity level in order to provide reproducible fluorescencemeasurement results.

At step 9010, color images of a sample gemstone are captured atdifferent image rotational angles while maintaining the image view angleconstant. At each image rotational angle, at least two images will becaptures of the gemstone: a regular image for when the gemstone isilluminated by a non-UV light source (e.g., a daylight approximatinglight source) and a fluorescence image for when the gemstone isilluminated by a UV light source (e.g., set at a predeterminedintensity).

In preferred embodiments, the angular difference between consecutivecolor images remains constant throughout the collection of all images.Any configurations disclosed herein (e.g., concerning image view anglesand image rotational angles) can be applied to the image collectionprocess. For example, if the camera is set up to take 30 pictures persecond and one full rotation of the sample platform takes 3 seconds, 90images will be collected after a full rotation. In some embodiments,platform surface completes at least a full rotation with respect to theimage capturing component. In some embodiments, the rotation is lessthan a full rotation. In some embodiments, the rotation is more than afull rotation; for example, 1.2 full rotations or less, 1.5 fullrotations or less, 1.8 full rotations or less, 2 full rotations or less,5 rotations, or 10 full rotations or less.

At step 9020, an outline mask is extracted for a non-UV illuminatedimage. Generally, an outline mask corresponds to the physical areaoccupied by a sample gemstone, represented by the full image of thesample gemstone. FIGS. 7A and 7B illustrate the differences for an imageof the same diamond, before and after an outline mask is applied. Asdepicted in FIG. 7B, the outline mask highlights and clearly defines theedges of the diamond such that parameters like width and height can bemore easily measured. The outline mask extraction process is done forall non-UV illuminated images taken for a given sample gemstone.

There are many methods for edge detection, and most of them can begrouped into two categories, search-based and zero-crossing based. Thesearch-based methods detect edges by first computing a measure of edgestrength, usually a first-order derivative expression such as thegradient magnitude, and then searching for local directional maxima ofthe gradient magnitude using a computed estimate of the localorientation of the edge, usually the gradient direction. Thezero-crossing based methods search for zero crossings in a second-orderderivative expression computed from the image in order to find edges,usually the zero-crossings of the Laplacian or the zero-crossings of anon-linear differential expression.

The edge detection methods known to date mainly differ in the types ofsmoothing filters that are applied and the way the measures of edgestrength are computed. As many edge detection methods rely on thecomputation of image gradients, they also differ in the types of filtersused for computing gradient estimates in the x- and y-directions.

Here, any applicable method for extracting an outline mask can be used,including for example an edge determining filter in commerciallyavailable software products such as Photoshop™ and etc. Additionally,for example, a simple algorithm can be developed in which any continuousareas in an image with a color value matching the background white color(as previously calibrated) is defined as black. As a result, acontinuous black area will form the outline mask with an openingcorresponding to the full image of a sample gemstone.

Based on outline masks, for each opening area corresponding to the fullimage of a sample gemstone, values of geometrical parameters (e.g., thewidth and height of the gemstone as illustrated in FIG. 7B) aredetermined. Outline masks are used for more accurate or automatedmeasurements of the geometrical parameters. Essentially, the geometricalparameters are determined based on each outline mask, or more precisely,the opening of each outline mask. The measurements are taken for eachimage. After this step, a plurality set of measurement values aredetermined for the plurality of color images (or their correspondingoutline masks), including, for example, a plurality if widthmeasurements and a plurality of height measurements.

At step 9030, an apparent fluorescence area is extracted from an imagecaptured under UV illumination for the same sample gemstone. Theapparent fluorescence area is defined by the extent of fluorescenceemission by portions of the sample gemstone that are capable of emittingfluorescence. As illustrated in FIGS. 7D and 7F, an apparentfluorescence area can be larger or smaller than the physical size of thegemstone. In particular, an apparent fluorescence area can benon-contiguous due to disconnected portions of the gemstones that emitfluorescence.

At steps 9040 through 9060, an apparent fluorescence area is overlaid ontop of the corresponding outline mask in order to identifying afluorescence mask. An important aspect of the overlaying step is toidentify part of the apparent fluorescence area that falls outside ofthe physical boundaries of a sample gemstone (as defined by an outlinemask). Because this part of the fluorescence emission does notcorrespond to any physical areas within the sample gemstone, includingit in assessing fluorescence likely leads to errors. As such, in someembodiments, when there is any fluorescence outside of the physicalboundaries of the sample gemstone, the corresponding fluorescenceoutside of the physical boundaries of the sample gemstone will beremoved in step 9050. In contrast, in other embodiments, when there isno fluorescence outside of the physical boundaries of the samplegemstone, a fluorescence mask can be directly computed at step 9060,usually as the apparent fluorescence area itself.

For example, in FIG. 7D(a), fluorescence is present through the entiregemstone resulting in a large and contiguous apparent fluorescence areadepicted in FIG. 7D(b). In this case, a fluorescence mask is a compositeof the outline mask and the apparent fluorescence area, obtained byremoving all areas beyond the physical boundaries of the sample gemstone(i.e., the outline mask). A fluorescence mask is identified byoverlaying the apparent fluorescence area onto the outline mask and thenremoving any fluorescence beyond the physical boundaries of the outlinemask. The fluorescence mask is the intersecting composition of theapparent fluorescence area and outline mask. In the particular example,because the apparent fluorescence area is contiguous and an outline maskis always contiguous, the resulting fluorescence mask is essentially theoutline mask, as outlined in steps 9050 and 9060. The scenarioillustrated in FIGS. 7E and 7F is a bit different. Here, fluorescence isemitted by disconnected parts of the sample gemstone, resulting in anon-contiguous apparent fluorescence area, as shown in FIG. 7F(b). Onceagain, a fluorescence mask is identified by overlaying the apparentfluorescence area onto the outline mask and then removing anyfluorescence beyond the physical boundaries of the outline mask. In thisparticular example, there is no fluorescence outside of the physicalboundaries of the sample gemstone (i.e., the outline mask). Theresulting fluorescence mask corresponds to the apparent fluorescencearea in FIG. 7F(b), as outlined in steps 9050 and 9060.

It will be understood that, if the extracted apparent fluorescence areais non-contiguous but also extends beyond the physical boundaries of thesample gemstone (i.e., the outline mask), the resulting fluorescencemask will be the apparent fluorescence area with the area outside theboundaries of the outline mask excluded (e.g., steps 9050 and 9060).Once again, the fluorescence mask is identified by overlaying theapparent fluorescence area; e.g., FIG. 7C(b), onto the outline mask forthe gemstone; e.g., FIG. 7D(b). Any area in the apparent fluorescencearea that is outside of the boundaries defined by the outline mask willbe eliminated. The remaining portion of the apparent fluorescence areaintersecting with the outline mask corresponds to the fluorescence mask.

In some embodiments, the fluorescence mask corresponds to 20% or less ofthe entire gemstone, 25% or less of the entire gemstone, 30% or less ofthe entire gemstone, 35% or less of the entire gemstone, 40% or less ofthe entire gemstone, 45% or less of the entire gemstone, 50% or less ofthe entire gemstone, 55% or less of the entire gemstone, 60% or less ofthe entire gemstone, 65% or less of the entire gemstone, 70% or less ofthe entire gemstone, 75% or less of the entire gemstone, 80% or less ofthe entire gemstone, 85% or less of the entire gemstone, 90% or less ofthe entire gemstone, or 100% or less of the entire gemstone. In someembodiments, the fluorescence mask corresponds to the entire physicalarea of the sample gemstone.

For improved accuracy and consistency, only pixels within thefluorescence mask will be subject to computation and further analysis(e.g., step 900). An exemplary data collection, computation and analysisprocess is illustrated in FIGS. 9B and 9C.

At step 910, a plurality of images are captured of a sample gemstoneunder non-UV illumination. The color images are captured at differentimage rotational angles while the image view angle remains constant.Considerations that affect data collection are all applicable.

At step 920, a plurality of fluorescent images are captured of a samplegemstone under UV illumination. The color images are captured atdifferent image rotational angles while the image view angle remainsconstant. Considerations that affect data collection are all applicable.The terms “fluorescent image” and “fluorescence image” will be usedinterchangeably.

At step 930, a fluorescence mask is applied to each fluorescence imagein the plurality of fluorescent images. Exemplary methods for computinga fluorescence mask has been illustrated in FIG. 9A and describedpreviously.

At step 940, pixels within the fluorescence mask are subject toquantitative analysis of the fluorescence images. For example, eachpixel can be analyzed to quantify the values of all color components inthe particular pixel. The number of color component is determined by thealgorithm according to which the pixel is encoded when the color imageis first captured. In some embodiments, the image is converted from itscapturing color mode (e.g., CMYK) to a different color mode (e.g., RGB).After values are quantified for each color component in each pixelwithin the fluorescence mask, an average value can be calculated foreach color component in a given fluorescence image. The process can berepeated for all images to calculate average value of each colorcomponent in all fluorescence images. Eventually, a final average valuecan be calculated for each color component based on information from allfluorescence images.

At step 950, the conversion process is carried out for all pixels withina defined area in an image in order to calculate average values of theone or more parameters. The steps of 910-950 can be repeated for allimages in the plurality of color images. Eventually, average values ofthe one or more parameters (e.g., L*, a*, and b*) can be calculated foreach color component based on information from all images.

At step 960, a first fluorescence score is calculated based on thevalues of the one or more parameters. For example, here the firstfluorescence score can be chroma (C*) and hue (h) values, calculatedbased on CIE color space values (e.g., L*, a*, and b*); e.g., based onthe following equations (FIG. 10):

$C*=\sqrt{{{{\left( a \right.{*)}}^{2} + \left( b \right.}{*)}}^{2}}$$h = {\tan^{- 1}\left( \frac{b*}{a*} \right)}$

In some embodiments, color images are analyzed using the standards(e.g., tables of color matching functions and illuminants as a functionof wavelength) published by CIE. A plot of the standard daylightilluminant with a correlated color temperature of 6500 K, D₆₅. Thisilluminant is represented here by the function H_(D65)(λ). The colormatching functions: x(λ), y(λ), z(λ) are used to calculate colorimetryparameters.

In some embodiments, the first fluorescence score represents the coloror hue characteristics of the fluorescence emitted by the samplegemstone.

FIG. 9C continues to illustrate an exemplary process for fluorescencegrade analysis. At step 962, individual color components in each pixelwithin the physical area of the gemstone in a fluorescent image (e.g.,defined by the corresponding outline mask) are quantified. In someembodiments, each pixel is broken into three values representing thecolors red (R), green (G) and blue (B). In some embodiments, each pixelis broken into three values representing the colors cyan (C), magenta(M), yellow (Y) and black (K). In some embodiments, the image isconverted from its capturing color mode (e.g., CMYK) to a differentcolor mode (e.g., RGB), or vice versa. The individual color componentsare then used to compute one or more parameters, for example, CIE colorspace values (e.g., L*, a*, and b*).

At step 964, the one or more parameters (e.g., L*, a*, and b*) arecomputed for all fluorescent images collected for a particular gemstoneduring one session (e.g., under the same illumination conditions whilethe image capture component (e.g., a camera) is configured under thesame setting.

At step 970, a second fluorescence score is calculated for the samegemstone. In some embodiments, the second fluorescence score representsthe fluorescence intensity of the gemstone. In some embodiments, thesecond fluorescence score represents the average fluorescence intensityof the gemstone according to the all the fluorescence images taken; forexample, the average L* value.

At step 980, values of the first and/or second fluorescence scores,e.g., L*, C*, h* are compared to previously determined standard valuesof corresponding control gemstones to assign a fluorescence grade to thesample gemstone. The previously determined standard values are obtainedfor control gemstones using the same or a similar process. For example,one or more sets of sample stones, which share the same or similarcolor, proportion or shape characteristic and whose fluorescence gradingvalues have been previously determined, are used as the controlgemstones or grading standards. In some embodiments, the fluorescencecolor is evident. In some embodiments, the fluorescence color can be tooweak for accurate identification. In such cases, the first and/or secondfluorescence scores of the sample gemstone can be compared with multiplesets of control gemstones, each of a different color.

An example of computing color characteristics (e.g., L*, a* and b*) isas follows. As diamond is a transparent material, the sum oftransmission spectrum T(λ) and reflection spectrum R(λ) is used in thecalculation of the tristimulus values, X, Y and Z:

X=Σ _(λ=380) ⁷⁸⁰ H _(D65)(λ)(T(λ)+R(λ)) x (λ)

Y=Σ _(λ=380) ⁷⁸⁰ H _(D65)(λ)(T(λ)+R(λ)) y (λ)

Z=Σ _(λ=380) ⁷⁹⁰ H _(D65)(λ)(T(λ)+R(λ)) z (λ).

The chromaticity coordinates, x and y, are then defined as:

$x = \frac{X}{X + Y + Z}$ $y = \frac{Y}{X + Y + Z}$

An attempt to achieve a “perceptually uniform” colour space is the CIE1976 colour space, otherwise known as the CIELAB colour space. Itsparameters are calculated from the tristimulus values as follows:

${ligntness},{L*={{116\left( {Y/Y_{W}} \right)^{\frac{1}{3}}} - 16}}$${{red}\text{-}{green}\mspace{14mu} {parameter}},{a*={500\left\lbrack {\left( {X/X_{W}} \right)^{\frac{1}{3}} - \left( {Y/Y_{W}} \right)^{\frac{1}{3}}} \right\rbrack}}$${{and}\mspace{14mu} {yellow}\text{-}{blue}\mspace{14mu} {parameter}},{b*={200\left\lbrack {\left( {Y/Y_{W}} \right)^{\frac{1}{3}} - \left( {Z/Z_{W}} \right)^{\frac{1}{3}}} \right\rbrack}},$

where X_(W), Y_(W) and Z_(W) are the tristimulus values for the whitepoint corresponding to the chosen illuminant, in this case D65.

$X_{W} = {\sum\limits_{\lambda = 380}^{780}{{H_{D\; 65}(\lambda)}{\overset{\_}{x}(\lambda)}}}$$Y_{W} = {\sum\limits_{\lambda = 380}^{780}{{H_{D\; 65}(\lambda)}{\overset{\_}{y}(\lambda)}}}$$Z_{W} = {\sum\limits_{\lambda = 380}^{780}{{H_{D\; 65}(\lambda)}{\overset{\_}{z}(\lambda)}}}$

The saturation or chroma is expressed as:

$C_{ab}^{*} = \left( {a^{*2} + b^{*2}} \right)^{\frac{1}{3}}$

and the hue angle is expressed as: h_(ab)=tan⁻¹(b*/a*).

Sources are available for image/color conversion and transformation. Forexample the Open CV project hosted at the docs<dot>opencv<dot>org can beused to convert RGB values to CIE L, a, b values. In addition, the sameor similar resources allows conversion between RGB values andhue-saturation-value (HSV) values, between RGB values andhue-saturation-lightness (HSL) values, between RGB values and CIE Luvvalues in the Adams chromatic valence color space.

The present invention can be implemented as a computer system and/or acomputer program product that comprises a computer program mechanismembedded in a computer readable storage medium. Further, any of themethods of the present invention can be implemented in one or morecomputers or computer systems. Further still, any of the methods of thepresent invention can be implemented in one or more computer programproducts. Some embodiments of the present invention provide a computersystem or a computer program product that encodes or has instructionsfor performing any or all of the methods disclosed herein. Suchmethods/instructions can be stored on a CD-ROM, DVD, magnetic diskstorage product, or any other computer readable data or program storageproduct. Such methods can also be embedded in permanent storage, such asROM, one or more programmable chips, or one or more application specificintegrated circuits (ASICs). Such permanent storage can be localized ina server, 802.11 access point, 802.11 wireless bridge/station, repeater,router, mobile phone, or other electronic devices. Such methods encodedin the computer program product can also be distributed electronically,via the Internet or otherwise, by transmission of a computer data signal(in which the software modules are embedded) either digitally or on acarrier wave.

Some embodiments of the present invention provide a computer system or acomputer program product that contains any or all of the program modulesas disclosed herein. These program modules can be stored on a CD-ROM,DVD, magnetic disk storage product, or any other computer readable dataor program storage product. The program modules can also be embedded inpermanent storage, such as ROM, one or more programmable chips, or oneor more application specific integrated circuits (ASICs). Such permanentstorage can be localized in a server, 802.11 access point, 802.11wireless bridge/station, repeater, router, mobile phone, or otherelectronic devices. The software modules in the computer program productcan also be distributed electronically, via the Internet or otherwise,by transmission of a computer data signal (in which the software modulesare embedded) either digitally or on a carrier wave.

Having described the invention in detail, it will be apparent thatmodifications, variations, and equivalent embodiments are possiblewithout departing the scope of the invention defined in the appendedclaims. Furthermore, it should be appreciated that all examples in thepresent disclosure are provided as non-limiting examples.

EXAMPLES

The following non-limiting examples are provided to further illustrateembodiments of the invention disclosed herein. It should be appreciatedby those of skill in the art that the techniques disclosed in theexamples that follow represent approaches that have been found tofunction well in the practice of the invention, and thus can beconsidered to constitute examples of modes for its practice. However,those of skill in the art should, in light of the present disclosure,appreciate that many changes can be made in the specific embodimentsthat are disclosed and still obtain a like or similar result withoutdeparting from the spirit and scope of the invention.

Example 1 Fluorescence Grading for Regular Stones

FIG. 10 shows images of a sample gemstone taken under both daylightapproximately light source (top 3 images) and under UV illumination(bottom 3 images). Under UV illumination, portions within the gemstonethat emit fluorescence at different strength are evident.

Example 2 Validation of Fluorescence Emission Levels in Reference Stones

In this example, 4 reference stones with different strengths influorescence emission were subject to analysis. Image view angle was setat 32 degree. A Point Grey GS3-U3-28S5C camera was used to capture theimages under regular and UV illuminations. Here, top UV illumination wasprovided by UV LEDs in combination with a band-pass filter andcollimation lens.

FIG. 11 illustrates that, with the except of C values, both L and hvalues (in particular L values) correlate with the strengths offluorescence emission observed in the reference stones.

Example 3 Gemstone with Inhomogeneous Fluorescence Distribution

Images in FIG. 12 show a gemstone with inhomogeneous fluorescencedistribution. At different image rotational angles (0 degree, 120 degreeand 240 degree), different levels of fluorescence emission wereobserved. When each image was evaluated individually, the resulting L,C, H values suggested different machine grading of fluorescencestrength. However, when L, C, H values were computed by averaging theeffects from all images, machine grading score and visual inspectiongrading score became consistent.

Example 4 Fancy Shaped Stones with Blue Fluorescence

FIG. 13 depicts gemstones of fancy shapes but all with bluefluorescence. Here, image view angle was set at 32 degree. A Point GreyGS3-U3-28S5C camera was used to capture the images under regular and UVilluminations. Here, top UV illumination was provided.

The stones were of different shapes and sizes. After applying theanalysis disclosed herein, the resulting machine fluorescence gradingscore for each stone was the same as the fluorescence grading scoreprovided by human visual inspection. Here, the stones emitted bluefluorescence at different levels.

Example 5 Gemstones with Different Fluorescence Colors

FIG. 14 depicts two gemstones emitting different fluorescence color: theone on the left side emitted green fluorescence while the one on theright side emitted yellow fluorescence. Here, image view angle was setat 32 degree. A Point Grey GS3-U3-28S5C camera was used to capture theimages under regular and UV illuminations. Here, top UV illumination wasprovided.

Again, after applying the analysis disclosed herein, the resultingmachine fluorescence grading score for each stone was the same as thefluorescence grading score provided by human visual inspection. Here,the stones emitted different colors of fluorescence.

Example 6 Gemstones with Different Sizes and Fluorescence Colors

FIG. 15 depicts two gemstones emitting different fluorescence color: theone on the left side emitted yellow fluorescence while the one on theright side emitted orange fluorescence. Here, image view angle was setat 20 degree. A Point Grey GS3-U3-28S5C camera was used to capture theimages under regular and UV illuminations. Here, top UV illumination wasprovided.

After applying the analysis disclosed herein, the resulting machinefluorescence grading score for each stone was the same as thefluorescence grading score provided by human visual inspection. Here,the two sample stones had drastically different sizes: one is almostthree times as big as the other. In addition, the stones emitteddifferent colors of fluorescence.

The various methods and techniques described above provide a number ofways to carry out the invention. Of course, it is to be understood thatnot necessarily all objectives or advantages described may be achievedin accordance with any particular embodiment described herein. Thus, forexample, those skilled in the art will recognize that the methods can beperformed in a manner that achieves or optimizes one advantage or groupof advantages as taught herein without necessarily achieving otherobjectives or advantages as may be taught or suggested herein. A varietyof advantageous and disadvantageous alternatives are mentioned herein.It is to be understood that some preferred embodiments specificallyinclude one, another, or several advantageous features, while othersspecifically exclude one, another, or several disadvantageous features,while still others specifically mitigate a present disadvantageousfeature by inclusion of one, another, or several advantageous features.

Furthermore, the skilled artisan will recognize the applicability ofvarious features from different embodiments. Similarly, the variouselements, features and steps discussed above, as well as other knownequivalents for each such element, feature or step, can be mixed andmatched by one of ordinary skill in this art to perform methods inaccordance with principles described herein. Among the various elements,features, and steps some will be specifically included and othersspecifically excluded in diverse embodiments.

Although the invention has been disclosed in the context of certainembodiments and examples, it will be understood by those skilled in theart that the embodiments of the invention extend beyond the specificallydisclosed embodiments to other alternative embodiments and/or uses andmodifications and equivalents thereof.

Many variations and alternative elements have been disclosed inembodiments of the present invention. Still further variations andalternate elements will be apparent to one of skill in the art.

In some embodiments, the numbers expressing quantities of ingredients,properties such as molecular weight, reaction conditions, and so forth,used to describe and claim certain embodiments of the invention are tobe understood as being modified in some instances by the term “about.”Accordingly, in some embodiments, the numerical parameters set forth inthe written description and attached claims are approximations that canvary depending upon the desired properties sought to be obtained by aparticular embodiment. In some embodiments, the numerical parametersshould be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof some embodiments of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspracticable. The numerical values presented in some embodiments of theinvention may contain certain errors necessarily resulting from thestandard deviation found in their respective testing measurements.

In some embodiments, the terms “a” and “an” and “the” and similarreferences used in the context of describing a particular embodiment ofthe invention (especially in the context of certain of the followingclaims) can be construed to cover both the singular and the plural. Therecitation of ranges of values herein is merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g. “such as”) provided with respectto certain embodiments herein is intended merely to better illuminatethe invention and does not pose a limitation on the scope of theinvention otherwise claimed. No language in the specification should beconstrued as indicating any non-claimed element essential to thepractice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember can be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. One ormore members of a group can be included in, or deleted from, a group forreasons of convenience and/or patentability. When any such inclusion ordeletion occurs, the specification is herein deemed to contain the groupas modified thus fulfilling the written description of all Markushgroups used in the appended claims.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations on those preferred embodiments will become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Itis contemplated that skilled artisans can employ such variations asappropriate, and the invention can be practiced otherwise thanspecifically described herein. Accordingly, many embodiments of thisinvention include all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Furthermore, numerous references have been made to patents and printedpublications throughout this specification. Each of the above citedreferences and printed publications are herein individually incorporatedby reference in their entirety.

In closing, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that can be employed can be within thescope of the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention can be utilized inaccordance with the teachings herein. Accordingly, embodiments of thepresent invention are not limited to that precisely as shown anddescribed.

We claim:
 1. An apparatus for assessing a fluorescence characteristic ofa gemstone, comprising: an optically opaque platform, wherein theplatform has a surface configured to support a gemstone to be assessed;a light source shaped to at least partially enclose the platform,wherein the light source is about the same level as or below the surfaceof platform and designed to provide uniform ultraviolet (UV) radiationto the gemstone on the platform; an image capturing component, whereinthe image capturing component is positioned at a predetermined anglerelative to the platform surface that supports the gemstone, and whereinthe image capturing component and platform are configured to rotaterelative to each other; and a telecentric lens positioned to provide animage of the illuminated gemstone to the image capturing component. 2.The apparatus of claim 1, further comprising: a reflector device havingan inner surface that is at least partially spherical and comprises areflective material, wherein the reflector device at least partiallycovers the light source and platform surface, and directs UV radiationfrom the light source towards the gemstone positioned on the platformsurface.
 3. The apparatus of claim 2, wherein the inner surface of thereflector device has a hemispherical shape.
 4. An apparatus forassessing a color characteristic of a gemstone, comprising: an opticallyopaque platform, wherein the platform has a surface configured tosupport a gemstone to be assessed; a light source above the surface ofthe platform, wherein the light source is designed to provide uniformultraviolet (UV) radiation to the gemstone on the platform; an imagecapturing component, wherein the image capturing component is positionedat a predetermined angle relative to the platform surface that supportsthe gemstone, and wherein the image capturing component and platform areconfigured to rotate relative to each other; and a telecentric lenspositioned to provide an image of the illuminated gemstone to the imagecapturing component.
 5. The apparatus of claim 4, further comprising: acollimation lens, wherein the collimation lens and the light source arecoupled to provide uniform UV illumination to the gemstone on theplatform.
 6. The apparatus of claim 4, further comprising: an opticaldiffuser, wherein the optical diffuser and the light source are coupledto provide uniform UV illumination to the gemstone on the platform. 7.The apparatus of claim 4, further comprising: a collimation lens, and anoptical diffuser, wherein the collimation lens, optical diffuser and thelight source are coupled to provide uniform UV illumination to thegemstone on the platform.
 8. The apparatus of claim 1, wherein the UVradiation provided by the light source comprises trans-radiation,direct-UV radiation, and a combination thereof.
 9. The apparatus ofclaim 1, wherein the light source further provides uniform non-UVillumination to the gemstone.
 10. The apparatus of claim 1, wherein thetelecentric lens is an object-space telecentric lens or a doubletelecentric lens.
 11. The apparatus of claim 1, wherein the platform isconfigured to rotate around a rotational axis that is perpendicular tothe side of the platform where the gemstone is positioned.
 12. Theapparatus of claim 8, wherein the platform is configured to rotate 360degrees around the rotational axis.
 13. The apparatus of claim 8,wherein the platform is a flat circular platform, and wherein therotational axis is through the center of the circular platform.
 14. Theapparatus of claim 1, wherein the platform surface comprises a UVreflective material.
 15. The apparatus of claim 1, wherein the platformsurface comprises a diffuse UV reflective material.
 16. The apparatus ofclaim 1, wherein the platform surface comprises a white diffusereflective material.
 17. The apparatus of claim 1, wherein the lightsource is configured as a ring light surrounding the platform surface.18. The apparatus of claim 1, wherein the light source comprises aplurality of light emitting LEDs.
 19. The apparatus of claim 18, whereinthe LEDs emits fluorescence at 365 nm or 385 nm.
 20. The apparatus ofclaim 18, wherein the LEDs are coupled with a bandpass filter.
 21. Theapparatus of claim 20, wherein the bandpass filter is set at 365 nm or385 nm.
 22. The apparatus of claim 21, wherein the LEDs are configuredas a ring light surrounding the platform surface.
 23. The apparatus ofclaim 1 wherein the light source comprises a daylight approximatinglight source and a plurality of light emitting LEDs.
 24. The apparatusof claim 23, wherein the LEDs are coupled with a bandpass filter. 25.The apparatus of claim 24, wherein the bandpass filter is set at 365 nmor 385 nm.
 26. The apparatus of claim 1, wherein the predetermined anglebetween the image capturing component and the platform surface isbetween approximately zero and approximately 45 degrees.
 27. Theapparatus of claim 1, wherein the predetermined angle between the imagecapturing component and the platform surface is between approximately 10and approximately 35 degrees.
 28. The apparatus of claim 1, wherein theimage capturing component is selected from the group consisting of acolor camera, a CCD camera, and one or more CMOS sensors.
 29. Theapparatus of claim 1, wherein the image capturing component a pluralityof color images of the gemstone illuminated by UV radiation, each imagecomprising a full image of the gemstone.
 30. The apparatus of claim 1,wherein the image capturing component captures a plurality of colorimages of the illuminated gemstone, wherein each image is taken when theimage capturing component and the platform surface are at a differentrelative rotational position, and wherein each image comprises a fullimage of the gemstone.
 31. The apparatus of claim 30, wherein theplurality of color images comprises 4 or more color images, 5 or morecolor images, 10 or more images, 15 or more images, 20 or more images,or 800 or more images, and wherein each image is taken at a unique imageangle and comprises a plurality of pixels.
 32. The apparatus of claim 1,further comprising: a computer readable medium for storing the imagescollected by the image capturing component.
 33. The apparatus of claim1, wherein the fluorescence characteristic is a fluorescence intensitylevel, a fluorescence color, or a combination thereof.
 34. The apparatusof claim 1, further comprising: an interface between the light sourceand platform surface for adjusting the output intensity of the UVradiation.
 35. The apparatus of claim 1, further comprising: a UV filterbetween the image capturing component and the telecentric lens toeliminate all UV components.
 36. A method of assessing a fluorescencecharacteristic of a sample gemstone, comprising: (i) determining afluorescence mask for a fluorescent image in a plurality of fluorescentimages based on an outline mask determined from an image in a pluralityof images and an apparent fluorescence area based on the fluorescentimage, wherein each image of the plurality of images comprises a fullimage of the sample gemstone being illuminated by non-UV light source,wherein each image of the plurality of fluorescent images comprises afull image of the sample gemstone being illuminated by uniform UV lightsource, and wherein the image and the fluorescent image are capturedunder identical conditions except the illumination light source; (ii)quantifying individual color components in each pixel in thefluorescence mask in the fluorescent image of the plurality offluorescent images, thereby converting values for individual colorcomponents to one or more parameters representing the colorcharacteristic of each pixel; (iii) determining an average value foreach of the one or more parameters for all pixels in the defined area inall images of the plurality of fluorescent image; and (iv) calculating afirst fluorescence score of a sample gemstone based on the averagevalues of the one or more parameters of all pixels in the defined areain all images of the plurality of fluorescent images.
 37. The method ofclaim 36, further comprising: (v) calculating a second fluorescencescore of a sample gemstone based on pixels in the outline masks for allimages of the plurality of fluorescent images.
 38. The method of claim37, further comprising: (vi) assessing the fluorescence characteristicof the sample gemstone by comparing the first or second fluorescencescore to values of corresponding fluorescence scores of one or morecontrol fluorescence gemstones which are previously determined.
 39. Themethod of claim 37, wherein the first fluorescence score reflects thecolor of the fluorescence and wherein the second fluorescence scorereflects the strength.
 40. The method of claim 36, further comprising:collecting the plurality of images of the sample gemstone using an imagecapturing component at uniquely different image rotational angles whilemaintaining a constant image view angle.
 41. The method of claim 36,further comprising: collecting the plurality of fluorescent images ofthe sample gemstone using an image capturing component at uniquelydifferent image rotational angles while maintaining a constant imageview angle, wherein each fluorescent image in the plurality offluorescent images corresponds to an image in the plurality of image andboth are captured under identical image rotational angle and image viewangle.
 42. The method of claim 36, further comprising: determining afluorescence mask for each fluorescent image in the plurality offluorescent images.
 43. The method of claim 42, further comprising:quantifying individual color components in each pixel in thefluorescence mask in each fluorescent image of the plurality offluorescent images.
 44. The method of claim 41, further comprising:collecting a new plurality of fluorescent images of the sample gemstoneusing the image capturing component at the uniquely different imagerotational angles while maintaining the constant image view angle,wherein there is a time gap between the time when the plurality offluorescent images is collected and the time when the new plurality offluorescent images is collected; assigning a new fluorescent grade basedon the new plurality of fluorescent images by applying steps (i) through(vi); and comparing the fluorescent grade and the new fluorescent gradebased on the time gap.
 45. The method of claim 44, wherein the time gapis between 2 minutes and 5 hours.